ORIGINAL: kahloq
Im using JR DS821's most everywhere on the CMP ME-109. I have the H9 1.50 P-51 with a saito 220 in it and although nice servos, the JR126mgs arent necessary. Nothing wrong with using them, but in quantity, will add up to a sizeable cost. My P-51 has the DS821's all around(except the throttle and the rudder servo).
Please note, I highly recommend NOT using a digital servo for the throttle servo. I have had three planes with digital servos on the throttle and all three failed. One causing the loss of the plane, another bunrt out after the first flight once the plane touched down thankfully, and the third caused the throttle to be stuck wide open forcing me to run the fuel out and deadstick the plane. Though I cannot stated this emplicitly, it seems that a digital servo is constantly trying to center itself and on the throttle, since its forced to stay in one position for extended lengths of time(say full throttle or 3/4), it overheats and can burn out.
I use JR126mg because I have a ton of them from my 1/5 scale warbirds that I've built and are currently building so I don't have to run out and get more servos. These servos only cost $34, just a few bucks more than the DS821. I like having the extra umph in my servos since I put all my birds through the test and a few extra bucks whon't kill you if you value your plane. I've seen some fatal crashes because some pilots didn't go the extra mile. I lost one last year to a servo vailure, complete loss, two years to build it and two mins to lose it.
I agree if your not going to push it, then they may be a bit much. I personally wouldn't want to go through another loss because I didn't want to spend the extra cash but the lesser servos will work just fine.
I agree that digital servos on the engine is just asking for trouble. I try to avoid them at all cost there. Just this weekend at the field, some poor guy lost his plane to some kinda glitch and all he used were digital servos.